Chemical mechanical polishing pad, manufacturing process thereof and chemical mechanical polishing method

ABSTRACT

A chemical mechanical polishing pad having a polishing surface with an arithmetic mean roughness (Ra) of 0.1 to 15 μm, a 10-point height (Rz) of 40 to 150 μm, a core roughness depth (Rk) of 12 to 50 μm and a reduced peak height (Rpk) of 7 to 40 μm, a manufacturing process thereof and a chemical mechanical polishing method. Even when the chemical mechanical polishing of a large-diameter wafer as an object to be polished is carried out by this pad, a polished surface having excellent in-plane uniformity and flatness can be formed.

FIELD OF THE INVENTION

The present invention relates to a chemical mechanical polishing pad, amanufacturing process thereof and a chemical mechanical polishingmethod.

More specifically, it relates to a chemical mechanical polishing padcapable of providing a polished surface having excellent in-planeuniformity and flatness when chemical mechanical polishing is made onthe surface, a manufacturing process thereof and a chemical mechanicalpolishing method using the above chemical mechanical polishing pad.

DESCRIPTION OF THE PRIOR ART

In the process for the manufacture of a semiconductor device, CMP(Chemical Mechanical Polishing) is employed as a technique capable ofproviding an extremely flat surface to a wafer. CMP is a technique forthe chemical mechanical polishing of a surface by letting chemicalmechanical polishing slurry which is an aqueous dispersion of abrasivegrains flow down over the surface of a chemical mechanical polishing padwhile the surface to be polished is pressed against and brought intoslide contact with the surface of the chemical mechanical polishing pad.It is known that the polishing result is greatly affected by theperformance characteristic and properties of the chemical mechanicalpolishing pad in this CMP.

There are known chemical mechanical polishing pads such as apolyurethane foamed resin pad containing a large number of pores and apad containing a large number of fine water-soluble particles dispersedin a nonfoamed matrix (the former is disclosed by JP-A 11-70463 and JP-A8-216029 and the latter is disclosed by JP-A 2000-34416, JP-A 2000-33552and JP-A 2001-334455) (the term “JP-A” as used herein means an“unexamined published Japanese patent application”).

Since the improvement of productivity is now desired in the process forthe manufacture of a semiconductor, a wafer which needs chemicalmechanical polishing is becoming larger in diameter.

When chemical mechanical polishing is made on a large-diameter wafer bya conventionally known method, the in-plane uniformity and flatness ofthe polished surface after chemical mechanical polishing may becomeunsatisfactory.

SUMMARY OF THE INVENTION

It is an object of the present invention which has been made in view ofthe above problem to provide a chemical mechanical polishing pad capableof providing a polished surface having excellent in-plane uniformity andflatness even when chemical mechanical polishing is made on alarge-diameter wafer as an object to be polished, a manufacturingprocess thereof and a chemical mechanical polishing method.

Other objects and advantages of the present invention will becomeapparent from the following description.

According to the present invention, firstly, the above objects andadvantages of the present invention are attained by a chemicalmechanical polishing pad having a polishing surface and a non-polishingsurface, the polishing surface having an arithmetic mean roughness (Ra)of 0.1 to 15 μm, a 10-point height (Rz) of 40 to 150 μm, a coreroughness depth (Rk) of 12 to 50 μm and a reduced peak height (Rpk) of 7to 40 μm.

Secondly, the above objects and advantages of the present invention areattained by a process of manufacturing the above chemical mechanicalpolishing pad, comprising the steps of:

-   -   molding a polishing layer; and    -   sanding at least the surface to be polishing surface of the        polishing layer.

Thirdly, the above objects and advantages of the present invention areattained by a chemical mechanical polishing method comprising chemicalmechanical polishing an object to be polished with the above chemicalmechanical polishing pad.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the definition of 10-point height (Rz);

FIG. 2 is a diagram showing the definition of a material ratio curve;

FIG. 3 is a diagram showing the definition of core roughness depth (Rk);and

FIG. 4 is a diagram showing the definition of reduced peak height (Rpk).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The polishing surface of the chemical mechanical polishing pad of thepresent invention has an arithmetic mean roughness (Ra) of 0.1 to 15 μm,a 10-point height (Rz) of 40 to 150 μm, a core roughness depth (Rk) of12 to 50 μm and a reduced peak height (Rpk) of 7 to 40 μm.

These values are defined as the averages of the following numericalvalues calculated from roughness profiles obtained by measuring aplurality of measurement lines set on the surface of the pad. Forexample, they can be calculated by a method disclosed by LM Manual(analog version), Version 3.62 published by Mitsuya Shoji Co., Ltd.

The arithmetic mean roughness (Ra) is a value expressed by the followingequation (1) when the x axis of the roughness profile of an evaluationlength L is plotted in the direction parallel to the mean line of theroughness profile, the y axis is plotted in the direction of thelongitudinal magnification of the roughness profile, and the measuredroughness profile is expressed by the equation y=f(x). $\begin{matrix}{{Ra} = {\frac{1}{L}{\int_{0}^{L}{{y}\quad{\mathbb{d}x}}}}} & (1)\end{matrix}$

The 10-point height (Rz) is a value expressed by the following equation(2) when the x axis of the roughness profile of the evaluation length Lis plotted in the direction parallel to the mean line of the roughnessprofile, they axis is plotted in the direction of the longitudinalmagnification of the roughness profile, the distances of the tops of thehighest mountain to the fifth highest mountain from the mean line in thedirection of the longitudinal magnification are represented by P1 to P5,and the distances to the bottoms of the lowest valley to the fifthlowest valley from the mean line are represented by V1 to V5,respectively (see FIG. 1). $\begin{matrix}{{Rz} = {\frac{1}{5}\left( {{\sum\limits_{i = 1}^{5}{Pi}} - {\sum\limits_{i = 1}^{5}{Vi}}} \right)}} & (2)\end{matrix}$

The core roughness depth (Rk) and the reduced peak height (Rpk) aredefined by a material ratio curve derived from the roughness profile ofthe evaluation length L.

The material ratio curve refers to a curve obtained by plotting asection level as the longitudinal axis and a material ratio as thehorizontal axis. The term “section level” used herein means a specificvalue of y when the roughness profile is expressed by the same equationy=f(x) as in the above arithmetic mean roughness (Ra). The term“material ratio” is a percentage of the length of a cut portion to theevaluation length L when the roughness profile is cut at a certainsection level. The material ratio is 0% when the section level is at thetop of the highest mountain in the roughness profile and 100% when thesection level is at the bottom of the lowest valley (see FIG. 2).

The core roughness depth (Rk) is a difference in section level betweenpoints C and D when two points A and B the difference in material ratiobetween which is 40% and the difference in section level between whichis the smallest are set on the material ratio curve defined as describedabove, the point C is the intersection between a straight lineconnecting the points A and B and extending in both-directions and aline representing a material ratio of 0%, and the point D is theintersection between the straight line connecting the points A and B anda line representing a material ratio of 100% (see FIG. 3).

The reduced peak height (Rpk) is a difference in section level betweenthe points C and J when the intersection between the section levelpassing through the point C in the definition of the above coreroughness depth (Rk) and the material ratio curve is a point H, theintersection between the material ratio curve and the line representinga material ratio of 0% is point I, and a point J is set on a straightline representing a material ratio of 0% to ensure that the areasurrounded by the line segment CH, line segment CI and the curve HIbecomes equal to the area of the triangle CHJ (see FIG. 4. A1 in FIG. 4is the area surrounded by the line segment CH, line segment CI and thecurve HI, that is, the area of the triangle CHJ).

A plurality of measurement lines for measuring the above arithmetic meanroughness (Ra), 10-point height (Rz), core roughness depth (Rk) andreduced peak height (Rpk) are set on the pad as follows.

First, the center points of the plurality of measurement lines are setas follows. As for the center points of the measurement lines, virtualstraight lines whose length becomes the longest are drawn from onearbitrary point at one end of the polishing surface of the pad toanother point (when the polishing surface of the pad is circular, theabove virtual straight lines become the diameter of a circle forming thepad surface) to set 10 to 50 points on the virtual straight lines atroughly equal intervals except for a 5% area of the length of thevirtual straight line from the center to the both sides and 5% areas ofthe length of the virtual straight line from the both ends. The numberof the center points of the measurement lines is preferably 25 to 50.

A groove(s) may be formed in the polishing surface of the chemicalmechanical polishing pad of the present invention as will be describedhereinafter. In this case, the center points of the measurement linesshould be set such that the all the measurement lines set as will bedescribed hereinafter are existent in a portion other than the groove(s)in the polishing surface. 10 to 50 measurement points may not be set atroughly equal intervals on the above virtual straight lines according tothe shape of the groove(s) formed in the polishing surface. In thiscase, out of the points set at equal intervals, the above number ofpoints may be secured by excluding the points of the measurement linespartially overlapping with the groove portion. Straight linesintersecting the virtual straight lines for setting the plurality ofpoints and passing through the “center points of the measurement lines”are assumed and taken as measurement lines. The length of themeasurement lines may be 1 to 15 mm with the center point of the abovemeasurement line as the center thereof.

The above roughness profile can be measured by using a commerciallyavailable surface roughness meter.

As for the chemical mechanical polishing pad of the present invention,the arithmetic mean roughness (Ra) of the polishing surface thusmeasured is 0.1 to 15 μm. This value is preferably 0.1 to 12 μm. The10-point height (Rz) is 40 to 150 μm. It is preferably 40 to 130 μm. Thecore roughness depth (Rk) is 12 to 50 μm. It is preferably 12 to 45 μm.The reduced peak height (Rpk) is 7 to 40 μm. It is preferably 7 to 30μm.

When the chemical mechanical polishing step is carried out by using thechemical mechanical polishing pad having these values, a polishedsurface having excellent in-plane uniformity and flatness can beobtained. This effect is marked particularly when a large-diameter waferis chemically mechanically polished.

The chemical mechanical polishing pad of the present inventionpreferably has a thickness distribution of 50 μm or less. The effect ofthe present invention is advantageously exhibited by setting thethickness distribution of the chemical mechanical polishing pad to 50 μmor less. This value is more preferably 40 μm or less, particularlypreferably 30 μm or less. By setting the thickness distribution of thechemical mechanical polishing pad to this range, even when alarge-diameter wafer as an object to be polished is chemicallymechanically polished, a polished surface having excellent in-planeuniformity and flatness can be obtained.

The thickness distribution can be calculated from the following equationby measuring the thickness at a plurality of measurement points set onthe surface of the pad.Thickness distribution=(largest measurement value ofthickness)−(smallest measurement value of thickness)

10 to 50 measurement points are set at equal intervals on virtualstraight lines drawn from one arbitrary point at one end of thepolishing surface of the pad to another point such that its lengthbecomes the largest (when the polishing surface of the pad is circular,the above virtual straight lines become the diameter of a circle formingthe pad surface) excluding a 5% area of the length of the virtualstraight line from the center to the both sides and 5% areas of thelength of the virtual straight line from the both ends. The number ofmeasurement points is preferably 25 to 50.

A groove(s) may be formed in the polishing surface of the chemicalmechanical polishing pad of the present invention as will be describedhereinafter. In this case, the measurement points should be set in aportion other than the groove(s) on the polishing surface. There is acase where 10 to 50 measurement points cannot be set at roughly equalintervals on the above virtual straight lines according to the shape ofthe groove(s) formed in the polishing surface. In this case, out of thepoints set at roughly equal intervals, the above number of measurementpoints may be secured by excluding points in the groove(s).

The thickness at each measurement point can be known by placing thechemical mechanical polishing pad on a horizontal plane and measuringthe distance between the measurement point and the horizontal plane. Acontact type distance meter may be used to measure the distance betweenthe measurement point and the horizontal plane. One of commerciallyavailable products of the above meter is Manual 3-D Meter (of MitutoyoCorporation).

The shape of the chemical mechanical polishing pad of the presentinvention is not particularly limited. It may be disk-like, belt-like orroller-like. Preferably, the shape of the chemical mechanical polishingpad is suitably selected according to a polishing machine. The size ofthe chemical mechanical polishing pad before use is not particularlylimited. A disk-like chemical mechanical polishing pad had a diameterof, for example, 0.5 to 500 cm, preferably 1.0 to 250 cm, morepreferably 20 to 200 cm. It has a thickness of, for example, more than0.1 mm and 100 mm or less, particularly preferably 1 to 10 mm.

The chemical mechanical polishing pad of the present invention may havea groove(s) or recessed portion(s) having an arbitrary shape in thepolishing surface. The groove(s) or recessed portion(s) serves to holdan aqueous dispersion for chemical mechanical polishing supplied duringchemical mechanical polishing and uniformly distribute it to thepolished surface of an object to be polished, retains wastes such aschips and polishing liquid waste generated by chemical mechanicalpolishing temporarily and becomes a route for discharging the wastes tothe outside.

The shape of the above groove(s) is not particularly limited but may becircular, lattice-like or radial. The shape of the above recessedportion(s) is circular or polygonal. The sectional form of the grobve(s)or recessed portion(s) is not particularly limited. It may be, forexample, rectangular, trapezoidal, U-shaped or V-shaped.

The number of the grooves or the recessed portions may be one or more.

The size of the above groove(s) or recessed portion(s) is notparticularly limited. The width of the groove(s) or the shortestdiameter of the recessed portion(s) may be, for example, 0.1 mm or more,specifically 0.1 to 0.5 mm, more specifically 0.2 to 3.0 mm. The depthof the groove(s) or the recessed portion(s) may be, for example, 0.1 mmor more, specifically 0.1 to 2.5 mm, more specifically 0.2 to 2.0 mm.

The surface roughness of the inner wall of the above groove(s) orrecessed portion(s) is preferably 20 μm or less, more preferably 15 μmor less. By setting the surface roughness of the inner wall of thegroove(s) or recessed portion(s) to this range, when chemical mechanicalpolishing is carried out with this pad, it is possible to prevent thepolished surface of the object from being scratched and to contribute tothe improvement of the polishing rate and the service life of thepolishing pad. The improvement of the polishing rate by setting thesurface roughness of the inner wall of the groove(s) or recessedportion(s) to the above range is assumed to be because the function ofdistributing an aqueous dispersion for chemical mechanical polishing tothe polished surface is carried out better. The improvement of theservice life of the polishing pad by setting the surface roughness ofthe inner wall of the groove(s) or recessed portion(s) to the aboverange is assumed to be because the function of discharging wastesgenerated by chemical mechanical polishing is carried out moreefficiently.

The above surface roughness can be measured with an optical surfaceroughness meter or contact type surface roughness meter. Examples of theabove optical surface roughness meter include a 3-D surface structuralanalytical microscope, scanning laser microscope and electron beamsurface form analyzer. Examples of the above contact type surfaceroughness meter include a tracer type surface roughness meter.

The chemical mechanical polishing pad of the present invention mayfurther have a groove(s) or recessed portion(s) on the non-polishingsurface (rear side of the pad).

The groove(s) or recessed portion(s) contributes to the suppression ofthe production of a surface defect on the polished surface in thechemical mechanical polishing step. It is assumed that even when foreignmatter such as coarse particles which may be contained in the aqueousdispersion for chemical mechanical polishing or cutting chips derivedfrom the production process of the chemical mechanical polishing padenter between the polishing pad and the object to be polished, therecessed portion(s) serves to ease excessively large pressure generatedlocally to thereby reduce the number of surface defects on the polishedsurface.

The shape of the above groove(s) or recessed portion(s) is notparticularly limited. The shape of the groove(s) may be spiral, annularor lattice-like. The shape of the recessed portion(s) may be circular orpolygonal.

The size of the groove(s) or recessed portion(s) may be arbitrary. Whenthe recessed portion(s) is/are circular, it/they may have a diameter of1 to 300 mm, specifically 5 to 200 mm, more specifically 10 to 150 mm.When the groove(s) is/are spiral, annular or lattice-like, it/they mayhave a width of 0.1 to 20 mm, specifically 0.1 to 10 mm. The depth ofthe groove(s) or recessed portion(s) may be, for example, 0.01 to 2.0mm, specifically 0.1 to 1.5 mm, more specifically 0.1 to 1.0 mmregardless of its/their shape.

The number of the grooves or recessed portions may one or more.

The chemical mechanical polishing pad of the present invention has athickness distribution of 50 μm or less as described above andoptionally has a groove(s) or recessed portion(s) in the polishingsurface and/or the non-polishing surface. Although the process formanufacturing the pad is not particularly limited, the pad can bemanufactured by a process comprising the following steps, for example.

-   -   (1) the step of preparing a composition for a chemical        mechanical polishing pad;    -   (2) the step of molding the above composition for a chemical        mechanical polishing pad into a polishing layer; and    -   (3) the step of sanding at least the polishing surface of the        above polishing layer.

A detailed description is subsequently given of each of the above steps.

(1) Step or Preparing a Composition for a Chemical Mechanical PolishingPad

The chemical mechanical polishing pad of the present invention may bemade of any material as far as the object of the present invention canbe attained. It is preferred that pores having the function of holdingan aqueous dispersion for chemical mechanical polishing during chemicalmechanical polishing and the function of retaining polishing chipstemporarily out of the functions of the chemical mechanical polishingpad should be formed by the time of polishing. Therefore, the chemicalmechanical polishing pad is preferably made of a material consisting ofwater-soluble particles and a water-insoluble matrix containing thewater-soluble particles dispersed therein, or a material consisting ofcavities and a water-insoluble matrix material containing the cavitiesdispersed therein, for example, a foam.

In the former material out of these, the water-soluble particles comeinto contact with an aqueous medium of slurry containing the aqueousmedium and a solid at the time of polishing and dissolve or swell to beeliminated, and the slurry can be held in pores formed by elimination.In the latter material, the slurry can be held in pores formed as thecavities.

The material of the above “water-insoluble matrix” is not particularlylimited but an organic material is preferred because it is easily moldedto have a predetermined shape and predetermined properties and canprovide suitable hardness and suitable elasticity. Examples of theorganic material include thermoplastic resins, elastomers, rubbers suchas crosslinked rubbers, and curable resins such as thermally oroptically curable resins and resins cured by heat or light. They may beused alone or in combination.

Out of these, the above thermoplastic resins include 1,2-polybutadieneresin, polyolefin resins such as polyethylene, polystyrene resins,polyacrylic resins such as (meth)acrylate-based resins, vinyl esterresins (excluding acrylic resins), polyester resins, polyamide resins,fluororesins such as polyvinylidene fluoride, polycarbonate resins andpolyacetal resins.

The above elastomers include diene elastomers such as 1,2-polybutadiene,polyolefin elastomer (TPO), styrene-based elastomers such asstyrene-butadiene-styrene block copolymer (SBS) and hydrogenated blockcopolymers thereof (SEBS), thermoplastic polyurethane elastomers (TPU),thermoplastic elastomers such as polyester elastomers (TPEE) andpolyamide elastomers (TPAE), silicone resin elastomers and fluororesinelastomers. The rubbers include conjugated diene rubbers such asbutadiene rubber (high cis-butadiene rubber, low cis-butadiene rubber,etc.), isoprene rubber, styrene-butadiene rubber and styrene-isoprenerubber, nitrile rubbers such as acrylonitrile-butadiene rubber, acrylicrubber, ethylene-α-olefin rubbers such as ethylene-propylene rubber andethylene-propylene-diene rubber, other rubbers such as butyl rubber,silicone rubber and fluorine rubber.

The above curable resins include urethane resins, epoxy resins, acrylicresins, unsaturated polyester resins, polyurethane-urea resins, urearesins, silicon resins, phenolic resins and vinyl ester resins.

The above organic materials may be modified by an acid anhydride group,carboxyl group, hydroxyl group, epoxy group or amino group. The affinityfor the water-soluble particles to be described hereinafter and slurryof the organic material can be adjusted by modification.

These organic materials may be used alone or in combination of two ormore.

Further, the organic material may be a partially or wholly crosslinkedpolymer or non-crosslinked polymer. Therefore, the water-insolublematrix may be composed of a crosslinked polymer alone, a mixture of acrosslinked polymer and a non-crosslinked polymer, or a non-crosslinkedpolymer alone. It is preferably composed of a crosslinked polymer aloneor a mixture of a crosslinked polymer and a non-crosslinked polymer.When a crosslinked polymer is contained, elastic recovery force isprovided to the water-insoluble matrix and displacement caused by shearstress applied to the chemical mechanical polishing pad during polishingcan be reduced. Further, it is possible to effectively prevent the poresfrom being plastically deformed by the excessive extension of thewater-insoluble matrix during polishing and dressing and the surface ofthe chemical mechanical polishing pad from being excessively napped.Therefore, the pores are formed efficiently even during dressing,whereby a reduction in the retainability of the slurry during polishingcan be suppressed and further the pad is rarely napped, thereby notimpairing polishing flatness. The method of crosslinking the abovematerial is not particularly limited. For example, chemical crosslinkingmaking use of an organic peroxide, sulfur or sulfur compound orradiation crosslinking by applying an electron beam may be employed.

The crosslinked polymer may be a crosslinked rubber, curable resin,crosslinked thermosetting resin or crosslinked elastomer out of theabove organic materials. Out of these, a crosslinked thermoplastic resinand/or crosslinked elastomer all of which are stable to a strong acid orstrong alkali contained in many kinds of slurry and are rarely softenedby water absorption are preferred. Out of the crosslinked thermoplasticresin and crosslinked elastomer, what is crosslinked with an organicperoxide is more preferred, and crosslinked 1,2-polybutadiene isparticularly preferred.

The content of the crosslinked polymer is not particularly limited butpreferably 30 vol % or more, more preferably 50 vol % or more,particularly preferably 70 vol % or more and may be 100 vol % of thewater-insoluble matrix. When the content of the crosslinked polymer inthe water-insoluble matrix is lower than 30 vol %, the effect obtainedby containing the crosslinked polymer may not be fully obtained.

The residual elongation after breakage (to be simply referred to as“residual elongation at break” hereinafter) of the above water-insolublematrix containing a crosslinked polymer can be 100% or less when aspecimen of the above water-insoluble matrix is broken at 80° C. inaccordance with JIS K 6251. That is, the total distance between benchmarks of the specimen after breakage becomes 2 times or less thedistance between the bench marks before breakage. This residualelongation at break is preferably 30% or less, more preferably 10% orless, particularly preferably 5% or less and generally 0% or more. Whenthe above residual elongation at break is higher than 100%, fine piecesscraped off from the surface of the chemical mechanical polishing pad orstretched at the time of polishing and surface renewal tend to fill thepores disadvantageously. The “residual elongation at break” is anelongation obtained by subtracting the distance between bench marksbefore the test from the total distance between each bench mark and thebroken portion of the broken and divided specimen in a tensile test inwhich a dumbbell-shaped specimen No. 3 is broken at a tensile rate of500 mm/min and a test temperature of 80° C. in accordance with the“vulcanized rubber tensile test method” specified in JIS K 6251. Thetest is carried out at 80° C. because heat is generated by slide contactat the time of actual polishing.

The above “water-soluble particles” are particles which are eliminatedfrom the water-insoluble matrix when they come into contact with slurryas an aqueous dispersion in the chemical mechanical polishing pad. Thiselimination may occur when they dissolve in water contained in theslurry upon their contact with water or when they swell and gel byabsorbing this water. Further, this dissolution or swelling is causednot only by their contact with water but also by their contact with anaqueous mixed medium containing an alcohol-based solvent such asmethanol.

The water-soluble particles have the effect of increasing theindentation hardness of the chemical mechanical polishing pad inaddition to the effect of forming pores. For example, the shore Dhardness of the chemical mechanical polishing pad of the presentinvention can be set to preferably 35 or more, more preferably 50 to 90,particularly preferably 60 to 85 and generally 100 or less by adding thewater-soluble particles. When the shore D hardness is 35 or more,pressure applied to the object to be polished can be increased, and thepolishing rate can be thereby improved. In addition, high polishingflatness is obtained. Therefore, the water-soluble particles areparticularly preferably made of a solid substance which can ensuresufficiently high indentation hardness for the chemical mechanicalpolishing pad.

The material of the water-soluble particles is not particularly limited.They are, for example, organic water-soluble particles or inorganicwater-soluble particles. Examples of the material for forming theorganic water-soluble particles include saccharides (polysaccharidessuch as starch, dextrin and cyclodextrin, lactose, mannitol, etc.),celluloses (such as hydroxypropyl cellulose, methyl cellulose, etc.),protein, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid,polyethylene oxide, water-soluble photosensitive resins, sulfonatedpolyisoprene and sulfonated polyisoprene copolymers. Examples of thematerial for forming the inorganic water-soluble particles includepotassium acetate, potassium nitrate, potassium carbonate, potassiumhydrogencarbonate, potassium chloride, potassium bromide, potassiumphosphate and magnesium nitrate. These water-soluble particles may beused alone or in combination of two or more. The water-soluble particlesmay be made of a predetermined single material, or two or more differentmaterials.

The water-soluble particles have an average particle diameter ofpreferably 0.1 to 500 μm, more preferably 0.5 to 100 μm. The pores areas big as preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm. Whenthe average particle diameter of the water-soluble particles is smallerthan 0.1 μm, the formed pores become smaller in size than the abrasivegrains in use, whereby a chemical mechanical polishing pad capable ofholding slurry completely may be hardly obtained. When the averageparticle diameter is larger than 500 μm, the formed pores become toobig, whereby the mechanical strength and polishing rate of the obtainedchemical mechanical polishing pad may lower.

The content of the water-soluble particles is preferably 1 to 90 vol %,more preferably 1 to 60 vol %, particularly preferably 2 to 40 vol %based on 100 vol % of the total of the water-insoluble matrix and thewater-soluble particles. When the content of the water-soluble particlesis lower than 1 vol %, pores are not fully formed in the obtainedchemical mechanical polishing pad and the polishing rate may lower. Whenthe content of the water-soluble particles is higher than 90 vol %, itmay be difficult to completely prevent the water-soluble particlesexistent in the interior of the obtained chemical mechanical polishingpad from swelling or dissolving, thereby making it difficult to maintainthe hardness and mechanical strength of the obtained chemical mechanicalpolishing pad at appropriate values.

It is preferred that the water-soluble particles should dissolve inwater only when they are exposed to the surface layer of the chemicalmechanical polishing pad and should not absorb moisture or swell whenthey are existent in the interior of the chemical mechanical polishingpad. Therefore, the water-soluble particles may have an outer shell forsuppressing moisture absorption on at least part of their outermostportion. This outer shell may be physically adsorbed to thewater-soluble particle, chemically bonded to the water-soluble particle,or in contact with the water-soluble particle by physical adsorption andchemical bonding. The outer shell is made of epoxy resin, polyimide,polyamide or polysilicate. Even when it is formed on only part of thewater-soluble particle, the above effect can be fully obtained.

The above water-insoluble matrix may contain a compatibilizing agent tocontrol its affinity for the water-soluble particles and thedispersibility of the water-soluble particles in the water-insolublematrix. Examples of the compatibilizing agent include homopolymers,block copolymers and random copolymers modified by an acid anhydridegroup, carboxyl group, hydroxyl group, epoxy group, oxazoline group oramino group, nonionic surfactants and coupling agents.

The water-insoluble matrix material constituting the chemical mechanicalpolishing pad comprising the latter water-insoluble matrix material(foam, etc.) containing cavities dispersed therein is, for example, apolyurehane, melamine resin, polyester, polysulfone or polyvinylacetate.

The average size of the cavities dispersed in the water-insoluble matrixmaterial is preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm.

There is a case where a chemical mechanical polishing pad comprising awater-insoluble matrix material containing cavities dispersed therein,for example, a foam may not satisfy the requirements for the arithmeticmean roughness (Ra), 10-point height (Rz), core roughness depth (Rk) andreduced peak height (Rpk) of the pad surface that the chemicalmechanical polishing pad of the present invention should have accordingto the sizes of the cavities. Therefore, the chemical mechanicalpolishing pad of the present invention preferably has a polishing layermade of a material consisting of water-soluble particles and awater-insoluble matrix containing the water-soluble particles dispersedtherein.

The method of obtaining the composition for a chemical mechanicalpolishing pad from the above material is not particularly limited. Forexample, the composition can be obtained by kneading together requiredmaterials including a predetermined organic material by means of akneader. A conventionally known kneader may be used, such as a roll,kneader, Banbury mixer or extruder (single-screw, multiple-screw).

The composition for a chemical mechanical polishing pad containingwater-soluble particles for obtaining a chemical mechanical polishingpad containing water-soluble particles can be obtained, for example, bykneading together a water-insoluble matrix, water-soluble particles andother additives. In general, they are kneaded together under heating sothat they can be easily processed at the time of kneading. Thewater-soluble particles are preferably solid at the kneadingtemperature. When they are solid, they can be dispersed with the abovepreferred average particle diameter irrespective of their compatibilitywith the water-insoluble matrix. Therefore, in this case, the type ofthe water-soluble particles is preferably selected according to theprocessing temperature of the water-insoluble matrix in use.

(2) Step of Molding a Polishing Layer from the Composition for aChemical Mechanical Polishing Pad

The method of forming a polishing layer which should become the chemicalmechanical polishing pad of the present invention is not particularlylimited. For example, the composition for a chemical mechanicalpolishing pad which will become a polishing layer is prepared and moldedinto a desired rough form to produce the polishing layer. At this point,a metal mold having a pattern which should become a groove(s) and/orrecessed portion(s) to be formed on the front surface and/or rearsurface of the polishing layer is used to mold the composition for achemical mechanical polishing pad, thereby making it possible to formthe groove(s) and/or recessed portion(s) together with the rough form ofthe polishing layer at the same time. When the groove(s) and/or recessedportion(s) are/is formed by molding, this step can be simplified and thesurface roughness of the inner wall of the groove(s) and/or recessedportion(s) can be made 20 μm or less easily.

The groove(s) and/or recessed portion(s) on the front surface and/orrear surface of the polishing layer may be formed by cutting orcounterboring after a polishing layer having none of them is produced.To form the groove(s) and/or recessed portion(s) by cutting orcounterboring, the step of forming the groove(s) and/orrecessed-portion(s) may be carried out before or after (3) the sandingstep which will be described next.

(3) Step of Sanding at Least the Polishing Surface of the AbovePolishing Layer

Thereafter, at least the polishing surface of the thus formed polishinglayer is sanded.

The term “sanding” means polishing with sandpaper. The sandpaper isobtained by bonding abrasive grains to a backing material such assheet-like or belt-like paper or cloth by an adhesive. The material ofthe abrasive grains is fine crystals of a natural mineral or fine grainsof an artificial inorganic compound. Examples of the natural mineralinclude emery and garnet and examples of the artificial inorganiccompound include aluminum oxide and silicon carbide.

The size of the abrasive grains used for the above sanding step ispreferably 20 to 200 μm, more preferably 25 to 150 μm. The grit size ofthe sandpaper is preferably 80 to 600, more preferably 120 to 400.

Sandpaper having a larger width than the polishing surface of the abovepolishing layer is preferably used for sanding.

Sanding can be carried out by fixing the above polishing layer on ahorizontal plane with the polishing surface facing up, bringing theentire polishing surface into contact with the sandpaper and moving thesandpaper relative to the polishing surface at a relative rate ofpreferably 0.1 to 100 m/min, more preferably 0.5 to 50 m/min. Thismovement may be rotational movement or linear movement with the contactportion between the polishing surface of the polishing layer and thesandpaper as a standard.

The amount of the polishing layer sanded out, that is, removed bysanding is preferably 0.05 to 3.0 mm, more preferably 0.1 to 2.0 mm.

Sanding may be carried out only with a single type of sandpaper or withdifferent types of sandpapers which differ in grit size in multiplestages. Out of these, sanding is preferably carried out with differenttypes of sandpapers which differ in grit size in multiple stages. Thenumber of stages is preferably 2 to 10, more preferably 3 to 6. Thethickness of the polishing layer sanded out, that is, removed in eachstage is preferably 0.01 to 1.5 mm, more preferably 0.1 to 1.0 mm. Whensanding is carried out with different types of sandpapers which differin grit size in multiple stages, a sandpaper having a larger grit sizeis preferably first used, followed by a sandpaper having a smaller gritsize.

The above sanding can be carried out by using a sandblasting apparatus,belt polishing machine, barrel polishing machine, puff polishingmachine, ring polishing machine, electrolytic polishing machine orelectrolytic and grain polishing machine. Out of these, a belt polishingmachine is preferably used. Commercially available products of the beltpolishing machine include the TS130D polishing machine of Amitec Co.,Ltd., the T-142DG wide belt sander of Kikukawa Tekkosho Co., Ltd., andthe wide belt sander of Meinan Machinery Works, Inc.

A chemical mechanical polishing pad having a thickness distribution of50 μm or less and a polishing surface with an arithmetic mean roughness(Ra) of 0.1 to 15 μm, a 10-point height (Rz) of 40 to 150 μm, a coreroughness depth (Rk) of 12 to 50 μm and a reduced peak height (Rpk) of 7to 40 μm can be easily obtained by carrying out this sanding.

A description is subsequently given of the chemical mechanical polishingmethod of the present invention.

The chemical mechanical polishing method of the present invention is thesame as a known chemical mechanical polishing method except that theabove chemical mechanical polishing pad of the present invention is setin a commercially available polishing machine.

The type of the surface to be polished is not particularly limited but ametal film, barrier metal film or insulating film which is a wirematerial may be used. Examples of the material of the above metal filminclude tungsten, aluminum, copper and alloys containing at least one ofthese metals. Examples of the material of the above barrier metal filminclude tantalum, titanium, tantalum nitride and titanium nitride.Examples of the material of the insulating film include silicon oxide.The type of the aqueous dispersion for chemical mechanical polishingshould be suitably selected according to the type of the surface to bepolished and the purpose of chemical mechanical polishing.

The object to be polished by the chemical mechanical polishing method ofthe present invention is preferably a semiconductor wafer having atleast one of the above materials on the surface to be polished. Althoughthe semiconductor wafer may be of any size, for the chemical mechanicalpolishing of a large-diameter semiconductor wafer, the advantage of thechemical mechanical polishing method of the present invention appearsmarkedly. The large-diameter semiconductor wafer means a semiconductorwafer having a diameter larger than 8 inches, preferably 10 inches ormore.

As described above, the chemical mechanical polishing pad of the presentinvention has an advantage that stability at the time of polishing awafer is increased by setting the surface roughness of the pad to acertain range. That is, with a conventionally known polishing pad,break-in dressing is necessary before a brand-new pad is set in thepolishing machine to polish a wafer. By setting the above surfaceroughness, stable polishing performance is obtained from the first waferafter the pad is set in the polishing machine without carrying outbreak-in dressing or by carrying out break-in dressing for a shorterperiod of time than in the prior art.

According to the present invention, there are provided a chemicalmechanical polishing pad which can provide a polished surface havingexcellent in-plane uniformity and flatness even when chemical mechanicalpolishing is made on a large-diameter wafer as an object-to be polished,a manufacturing process thereof and a chemical mechanical polishingmethod.

EXAMPLES Example 1

98 vol % of 1,2-polybutadiene (JSR RB830 of JSR Corporation) and 2 vol %of β-cyclodextrin (Dexy Pearl β-100 of Bio Research Corporation ofYokohama) as a water-soluble substance were kneaded together by anextruder heated at 155° C. Thereafter, Percumyl D40 (trade name,manufactured by NOF Corporation, containing 40% by mass of dicumylperoxide) was added in an amount of 1.0 part by mass (equivalent to 0.4parts by mass in terms of pure dicumyl peroxide) based on 100 parts bymass of 1,2-polybutadiene and further kneaded with the above kneadedproduct, and the resulting product was crosslinked in a press mold at170° C. for 18 minutes to obtain a disk-like molded product having adiameter of 810 cm and a thickness of 3.3 mm. This molded product wasset in the insertion port of a wide belt sanding apparatus (of MeinanMachinery Works, Inc.) and moved at a rate of 0.1 m/sec to sand thesurface of the molded product with sandpapers having grit sizes of 120,150, 220 and 320(of Novatec Co., Ltd.) by turning a roller at arevolution of 500 rpm to remove 0.04 mm from the surface with each step.As a result, a molded product having an average thickness of 2.5 mm, athickness distribution of 20 μm, an arithmetic mean roughness (Ra) of4.4 μm, a 10-point height (Rz) of 125 μm, a core roughness depth (Rk) of16 μm and a reduced peak height (Rpk) of 14 μm was obtained.

The relative speed between the molded product and the sandpaper on thecontact surface between the molded product and the sandpaper for abovesanding was 5 m/min.

The above thickness distribution was calculated based on the followingequation from thicknesses measured at 33 points equally apart from oneanother of the polishing surface of the molded product in the diameterdirection excluding a 40 mm area from the center to the both sides and40 mm areas from the both ends by the manual 3-D meter (of MitutoyoCorporation).Thickness distribution=(largest measurement value ofthickness)−(smallest measurement value of thickness)

The arithmetic mean roughness (Ra), 10-point height (Rz), core roughnessdepth (Rk) and reduced peak height (Rpk) are all average valuescalculated from the roughness profiles obtained by measuring 10measurement lines (evaluation length of 10 mm) perpendicular to thediameter direction of the pad with 10 points equally apart from oneanother in the diameter direction of the polishing surface of the moldedproduct excluding 40 mm areas from the both ends as the centers by the1LM21P of Laser Tech Co., Ltd.

Concentric grooves having a width of 0.5 mm, a pitch of 2 mm and a depthof 1.0 mm were formed in the sanded surface of the molded product with acutting machine (of Kato Machinery Co., Ltd.) to manufacture a chemicalmechanical polishing pad. The surface roughness of the inner walls ofthe grooves was 6 μm.

This chemical mechanical polishing pad was set in the Applied Reflexionchemical mechanical polishing machine of Applied Material Co., Ltd. tocarry out break-in dressing while deionized water was supplied under thefollowing conditions.

-   -   Revolution of platen: 120 rpm    -   Supply rate of deionized water: 100 ml/min    -   Polishing time: 600 seconds

Thereafter, chemical mechanical polishing was made on a 12-inch waferhaving a PETEOS film as an object to be polished under the followingconditions. The PETEOS film was a silicon oxide film formed fromtetraethyl silicate (TEOS) by a chemical vapor deposition method usingplasma as a promoting condition.

-   -   Revolution of platen: 120 rpm    -   Revolution of polishing head: 36 rpm    -   Polishing pressured:    -   Retainer ring pressure=7.5 psi    -   Pressure of zone 1=6.0 psi    -   Pressure of zone 2=3.0 psi    -   Pressure of zone 3=3.5 psi    -   Supply rate of aqueous dispersion: 300 ml/min    -   Polishing time: 60 seconds    -   Aqueous dispersion for chemical mechanical polishing:    -   CMS1101 (of JSR Corporation)

The thickness of the PETEOS film before and after chemical mechanicalpolishing was measured at 33 points equally apart from one another inthe diameter direction of the 12-inch wafer having a PETEOS filmexcluding 5 mm areas from the both ends as the object to be polished.The polishing rate and the in-plane uniformity were calculated from themeasurement results based on the following equation.Amount of polishing=thickness before polishing−thickness after polishingPolishing rate=Σ(amount of polishing)/polishing time In-plane uniformity(standard deviation of amount of polishing÷average amount ofpolishing)×100(%)

The results are shown in Table 1. It can be said that in-planeuniformity is satisfactory when the in-plane uniformity is 3% or less.

Example 2

A molded product having an average thickness of 2.5 mm, a thicknessdistribution of 20 μm, an arithmetic mean roughness (Ra) of 3.4 μm, a10-point height (Rz) of 108 μm, a core roughness depth (Rk) of 18 μm anda reduced peak height (Rpk) of 16 μm was obtained in the same manner asin Example 1 except that 80 vol % of 1,2-polybutadiene, 20 vol % ofβ-cyclodextrin and 0.8 part by mass (equivalent to 0.32 part by mass interms of pure dicumyl peroxide) of Percumyl D40 based on 100 parts bymass of 1,2-polybutadiene were used.

Concentric grooves having a width of 0.5 mm, a pitch of 2 mm, a depth of1.0 mm and a surface roughness of the inner wall of 5 μm were formed inthe sanded surface of the molded product in the same manner as inExample 1 to manufacture a chemical mechanical polishing pad.

Evaluations were made by using this chemical mechanical polishing pad inthe same manner as in Example 1. The results are shown in Table 1.

Example 3

A molded product having an average thickness of 2.5 mm, a thicknessdistribution of 25 μm, an arithmetic mean roughness (Ra) of 3.8 μm, a10-point height (Rz) of 115 μm, a core roughness depth (Rk) of 15 μm anda reduced peak height (Rpk) of 14 μm was obtained in the same manner asin Example 1 except that 64 vol % of 1,2-polybutadiene, 16 vol % of astyrene-butadiene block copolymer (TR2827 of JSR Corporation) and 20 vol% of β-cyclodextrin were used.

Concentric grooves having a width of 0.5 mm, a pitch of 2 mm, a depth of1.0 mm and a surface roughness of the inner wall of 4.5 μm were formedin the sanded surface of the molded product in the same manner as inExample 1 to manufacture a chemical mechanical polishing pad.

Evaluations were made by using this chemical mechanical polishing pad inthe same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1

A molded product having an average thickness of 2.5 mm, a thicknessdistribution of 70 μm, an arithmetic mean roughness (Ra) of 1.5 am, a10-point height (Rz) of 25 μm, a core roughness depth (Rk) of 8 μm and areduced peak height (Rpk) of 6 μm was obtained in the same manner as inExample 1 except that a mold having an average thickness of 2.5 mm wasused to obtain a molded product and the molded product was not sanded.

Concentric grooves having a width of 0.5 mm, a pitch of 2 mm, a depth of1.0 mm and a surface roughness of the inner wall of 5.5 μm were formedin the polishing surface of the molded product in the same manner as inExample 1 to manufacture a chemical mechanical polishing pad.

Evaluations were made by using this chemical mechanical polishing pad inthe same manner as in Example 1. The results are shown in Table 1. TABLE1 Polishing rate in-plane uniformity (Å/min) (%) Example 1 2850 1.0Example 2 2700 2.0 Example 3 2750 1.5 Comparative 2800 8.0 Example 1

Example 4

The chemical mechanical polishing of a 12-inch wafer having a PETEOSfilm was carried out in the same manner as in Example 1 except thatbreak-in dressing was not carried out. Subsequently, chemical mechanicalpolishing was made continuously on 10 12-inch wafers having a PETEOSfilm. The polishing rate of each wafer is shown in Table 2.

Comparative Example 2

Chemical mechanical polishing was made on 10 wafers in the same manneras in Example 4 except that the chemical mechanical polishing padmanufactured in the same manner as in Comparative Example 1 was used.The polishing rate of each wafer is shown in Table 2. TABLE 2 Polishingrate Polishing (Å/min) order of Comparative wafers Example 4 Example 2 12830 1830 2 2850 1850 3 2870 1910 4 2820 2100 5 2840 2510 6 2850 2840 72880 2860 8 2870 2870 9 2850 2840 10 2840 2830

1. A chemical mechanical polishing-pad having a polishing surface and anonpolishing surface, the polishing surface having an arithmetic meanroughness (Ra) of 0.1 to 15 μm, a 10-point height (Rz) of 40 to 150 μm,a core roughness depth (Rk) of 12 to 50 μm and a reduced peak height(Rpk) of 7 to 40 μm.
 2. The chemical mechanical polishing pad accordingto claim 1 having a thickness distribution of 50 μm or less.
 3. Aprocess of manufacturing the chemical mechanical polishing pad of claim1 or 2, comprising the steps of: molding a polishing layer; and sandingat least the surface to be polishing surface of the polishing layer. 4.A chemical mechanical polishing method comprising chemical mechanicalpolishing an object to be polished with the chemical mechanicalpolishing pad of claim 1 or 2.